To mount or remove an infant on-vehicle seat on and from a base with a safer and easier method by providing a first mounting mechanism and a second mounting mechanism as a mounting mechanism provided for infant carrying.

An infant carrying tool 14 is provided with a mounting mechanism 44 mountable on and removable from a base 12, and this mounting mechanism 44 is formed of a first mounting mechanism and a second mounting mechanism. The first mounting mechanism is provided with a semicircular sectional horizontal edge part 48 extending substantially straightly on the foot-side end of the infant carrying tool 14 received by a reverse J-shaped hook 50 extended upward from the foot-side end of the base 12. The second mounting mechanism is situated in the bottom part of the infant carrying tool 14 and provided with two substantially horizontal upward contact surfaces 58 separately provided on the head-side end of the infant carrying tool 14 and cooperating with a downward contact surface 60 adjacent to the head-side end. Further, the release mechanism by the operation of a user comprises a rotating block 66 rotatably supported on the head-side end of the infant carrying tool 14.